Systems and methods for beam angle adjustment in ion implanters

ABSTRACT

An ion implantation system employs a mass analyzer for both mass analysis and angle correction. An ion source generates an ion beam along a beam path. A mass analyzer is located downstream of the ion source that performs mass analysis and angle correction on the ion beam. A resolving aperture within an aperture assembly is located downstream of the mass analyzer component and along the beam path. The resolving aperture has a size and shape according to a selected mass resolution and a beam envelope of the ion beam. An angle measurement system is located downstream of the resolving aperture and obtains an angle of incidence value of the ion beam. A control system derives a magnetic field adjustment for the mass analyzer according to the angle of incidence value of the ion beam from the angle measurement system.

FIELD OF THE INVENTION

The present invention relates generally to ion implantation systems, andmore specifically to systems and methods for performing beam angleadjustments of ion beams in ion implantation systems.

BACKGROUND OF THE INVENTION

In the manufacture of semiconductor devices, ion implantation is used todope semiconductors with impurities or dopants. Ion beam implanters areused to treat silicon wafers with an ion beam, in order to produce n orp type extrinsic material doping or to form passivation layers duringfabrication of an integrated circuit. When used for dopingsemiconductors, the ion beam implanter injects a selected extrinsic ionspecies to produce the desired semiconducting material. Implanting ionsgenerated from source materials such as antimony, arsenic or phosphorusresults in “n type” extrinsic material wafers, whereas if “p type”extrinsic material wafers are desired, ions generated with sourcematerials such as boron, or indium may be implanted.

Typical ion beam implanters include an ion source for generatingpositively charged ions from ionizable source materials. The generatedions are formed into a beam and directed along a predetermined beam pathto an implantation station. The ion beam implanter may include beamforming and shaping structures extending between the ion source and theimplantation station. The beam forming and shaping structures maintainthe ion beam and bound an elongated interior cavity or passagewaythrough which the beam passes en route to the implantation station. Whenoperating an implanter, this passageway can be evacuated to reduce theprobability of ions being deflected from the predetermined beam path asa result of collisions with gas molecules.

Trajectories of charged particles of given kinetic energy in a magneticfield will differ for different masses (or charge-to-mass ratios) ofthese particles. Therefore, the part of an extracted ion beam whichreaches a desired area of a semiconductor wafer or other target afterpassing through a constant magnetic field can be made pure since ions ofundesirable molecular weight will be deflected to positions away fromthe beam and implantation of other than desired materials can beavoided. The process of selectively separating ions of desired andundesired charge-to-mass ratios is known as mass analysis. Massanalyzers typically employ a mass analysis magnet creating a dipolemagnetic field to deflect various ions in an ion beam via magneticdeflection in an arcuate passageway which will effectively separate ionsof different charge-to-mass ratios.

For some ion implantation systems, the physical size of the beam issmaller than a target workpiece, so the beam is scanned in one or moredirections in order to adequately cover a surface of the targetworkpiece. Generally, an electrostatic or magnetic based scanner scansthe ion beam in a fast direction and a mechanical device moves thetarget workpiece in a slow scan direction in order to provide sufficientcover.

Thereafter the ion beam is directed toward a target end station, whichholds a target workpiece. Ions within the ion beam implant into thetarget workpiece, which is ion implantation. One importantcharacteristic of ion implantation is that there exists a uniformangular distribution of ion flux across the surface of the targetworkpiece, such as a semiconductor wafer. The angular content of the ionbeam defines implant properties through crystal channeling effects orshadowing effects under vertical structures, such as photoresist masksor CMOS transistor gates. A non-uniform angular distribution or angularcontent of the ion beam can lead to uncontrolled and/or undesiredimplant properties.

Beam diagnostic equipment can be employed to measure the angle contentof ion beams. The measurement data can then be employed to adjust anglecharacteristics of the ion beam. However, conventional approaches canincrease complexity of the ion implantation system and undesirablyincrease the length of path along which the ion beam travels.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention, and is neitherintended to identify key or critical elements of the invention nor todelineate the scope of the invention. Rather, the purpose of the summaryis to present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented later.

Aspects of the present invention facilitate ion implantation byperforming angle adjustments without additional components being addedto ion implantation systems. The aspects employ a mass analyzer toperform selected angle adjustments during ion implantation instead ofemploying separate and/or additional components.

In accordance with one aspect of the invention, an ion implantationsystem employs a mass analyzer for both mass analysis and anglecorrection. An ion source generates an ion beam along a beam path. Amass analyzer is located downstream of the ion source that performs massanalysis and angle correction on the ion beam. A resolving aperturewithin an aperture assembly is located downstream of the mass analyzercomponent and along the beam path. The resolving aperture has a size andshape according to a selected mass resolution and a beam envelope of theion beam. An angle measurement system is located downstream of theresolving aperture and obtains an angle of incidence value of the ionbeam. A control system derives a magnetic field adjustment for the massanalyzer according to the angle of incidence value of the ion beam fromthe angle measurement system. Other systems and methods are disclosed.

The following description and annexed drawings set forth in detailcertain illustrative aspects and implementations of the invention. Theseare indicative of but a few of the various ways in which the principlesof the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example ion implantation system in accordance withan aspect of the present invention.

FIG. 2 is a diagram illustrating an ion implantation system employing amass analyzer for mass analysis and angle correction in accordance withan aspect of the present invention.

FIG. 3A is a view of a portion of an ion implantation system inaccordance with an aspect of the present invention wherein an ion beamtravels along a base or nominal path.

FIG. 3B is a view of a portion of an ion implantation system inaccordance with an aspect of the present invention wherein an ion beamtravels along an altered path.

FIG. 3C is another view of a portion of an ion implantation system inaccordance with an aspect of the present invention wherein an ion beamtravels along an altered path.

FIG. 4 is a side view of a resolving aperture assembly in accordancewith an aspect of the present invention.

FIG. 5 is a flow diagram of a method of adjusting the angle ofimplantation in accordance with an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to thedrawings wherein like reference numerals are used to refer to likeelements throughout, and wherein the illustrated structures are notnecessarily drawn to scale.

Aspects of the present invention facilitate ion implantation employing amass analyzer to perform angle correction/adjustment in addition to massanalysis. As a result, angle corrections of the implant angle can beperformed without additional components along the beam line.

FIG. 1 illustrates an example ion implantation system 110 in accordancewith an aspect of the present invention. The system 110 is presented forillustrative purposes and it is appreciated that aspects of theinvention are not limited to the described ion implantation system andthat other suitable ion implantation systems of varied configurationscan also be employed.

The system 110 has a terminal 112, a beamline assembly 114, and an endstation 116. The terminal 112 includes an ion source 120 powered by ahigh voltage power supply 122 that produces and directs an ion beam 124to the beamline assembly 114. The ion source 120 generates charged ionsthat are extracted and formed into the ion beam 124, which is directedalong a beam path in the beamline assembly 114 to the end station 116.

To generate the ions, a gas of a dopant material (not shown) to beionized is located within a generation chamber 121 of the ion source120. The dopant gas can, for example, be fed into the chamber 121 from agas source (not shown). In addition to power supply 122, it will beappreciated that any number of suitable mechanisms (none of which areshown) can be used to excite free electrons within the ion generationchamber 121, such as RF or microwave excitation sources, electron beaminjection sources, electromagnetic sources and/or a cathode whichcreates an arc discharge within the chamber, for example. The excitedelectrons collide with the dopant gas molecules and ions are generatedthereby. Typically, positive ions are generated although the disclosureherein is applicable to systems wherein negative ions are generated aswell.

The ions are controllably extracted through a slit 118 in the chamber121 by an ion extraction assembly 123, in this example. The ionextraction assembly 123 comprises a plurality of extraction and/orsuppression electrodes 125. The extraction assembly 123 can include, forexample, a separate extraction power supply (not shown) to bias theextraction and/or suppression electrodes 125 to accelerate the ions fromthe generation chamber 121. It can be appreciated that since the ionbeam 124 comprises like charged particles, the beam may have a tendencyto blow up or expand radially outwardly as the like charged particlesrepel one another. It can also be appreciated that beam blow up can beexacerbated in low energy, high current (high perveance) beams wheremany like charged particles (e.g., high current) are moving in the samedirection relatively slowly (e.g., low energy) such that there is anabundance of repulsive forces among the particles, but little particlemomentum to keep the particles moving in the direction of the beam path.Accordingly, the extraction assembly 123 is generally configured so thatthe beam is extracted at a high energy so that the beam does not blow up(e.g., so that the particles have sufficient momentum to overcomerepulsive forces that can lead to beam blow up). Moreover, the beam 124,in this example, is generally transferred at a relatively high energythroughout the system and is reduced just before the workpiece 130 topromote beam containment.

The beamline assembly 114 has a beamguide 132, a mass analyzer 126, ascanning system 135, and a parallelizer 139. The mass analyzer 126performs mass analysis and angle correction/adjustment on the ion beam124. The mass analyzer 126, in this example, is formed at about a ninetydegree angle and comprises one or more magnets (not shown) that serve toestablish a (dipole) magnetic field therein. As the beam 124 enters themass analyzer 126, it is correspondingly bent by the magnetic field suchthat ions of an inappropriate charge-to-mass ratio are rejected. Moreparticularly, ions having too great or too small a charge-to-mass ratioare deflected into side walls 127 of the mass analyzer 126. In thismanner, the mass analyzer 126 merely allows those ions in the beam 124which have the desired charge-to-mass ratio to pass there-through andexit through a resolving aperture 134 of an aperture assembly 133.

The mass analyzer 126 can perform angle corrections on the ion beam 124by controlling or adjusting an amplitude of the magnetic dipole field.This adjustment of the magnetic field causes selected ions having thedesired/selected charge-to-mass ratio to travel along a different oraltered path. As a result, the resolving aperture 134 can be adjustedaccording to the altered path. In one example, the aperture assembly 133is movable about an x direction so as to accommodate altered pathsthrough the aperture 134. In another example, the aperture 134 is shapedso as to accommodate a selected range of altered paths. The massanalyzer 126 and the resolving aperture 134 allow variations in themagnetic field and resulting altered path while maintaining suitablemass resolution for the system 110. More detailed examples of suitablemass analyzer and resolving aperture systems are provided below.

It will be appreciated that ion beam collisions with other particles inthe system 110 can degrade beam integrity. Accordingly, one or morepumps (not shown) may be included to evacuate, at least, the beamguide132 and mass analyzer 126.

The scanning system 135 in the illustrated example includes a magneticscanning element 136 and a focusing and/or steering element 138.Respective power supplies 149, 150 are operatively coupled to thescanning element 136 and the focusing and steering element 138, and moreparticularly to respective electromagnet pieces 136 a, 136 b andelectrodes 138 a, 138 b located therein. The focusing and steeringelement 138 receives the mass analyzed ion beam 124 having a relativelynarrow profile (e.g., a “pencil” beam in the illustrated system 110). Avoltage applied by the power supply 150 to the plates 138 a and 138 boperates to focus and steer the beam to the scan vertex 151 of thescanning element 136. A voltage waveform applied by the power supply 149(which theoretically could be the same supply as 150) to theelectromagnets 136 a and 136 b then scans the beam 124 back and forth,in this example. It will be appreciated that the scan vertex 151 can bedefined as the point in the optical path from which each beamlet orscanned part of the beam appears to originate after having been scannedby the scanning element 136.

The scanned beam 124 is then passed through the parallelizer/corrector139, which comprises two dipole magnets 139 a, 139 b in the illustratedexample. The dipoles are substantially trapezoidal and are oriented tomirror one another to cause the beam 124 to bend into a substantially sshape. Stated another way, the dipoles have equal angles and radii andopposite directions of curvature.

The parallelizer 139 causes the scanned beam 124 to alter its path suchthat the beam 124 travels parallel to a beam axis regardless of the scanangle. As a result, the implantation angle is relatively uniform acrossthe workpiece 130.

One or more deceleration stages 157 are located downstream of theparallelization component 139 in this example. Up to this point in thesystem 110, the beam 124 is generally transported at a relatively highenergy level to mitigate the propensity for beam blow up, which can beparticularly high where beam density is elevated such as at scan vertex151, for example. The deceleration stage 157 comprises one or moreelectrodes 157 a, 157 b operable to decelerate the beam 124. Theelectrodes 157 are typically apertures thru which the beam travels, maybe drawn as straight lines in FIG. 1.

Nevertheless, it will be appreciated that while two electrodes 125 a and125 b, 136 a and 136 b, 138 a and 138 b and 157 a and 157 b arerespectively illustrated in the exemplary ion extraction assembly 123,scanning element 136, focusing and steering element 138 and decelerationstage 157, that these elements 123, 136, 138 and 157 may comprise anysuitable number of electrodes arranged and biased to accelerate and/ordecelerate ions, as well as to focus, bend, deflect, converge, diverge,scan, parallelize and/or decontaminate the ion beam 124 such as providedin U.S. Pat. No. 6,777,696 to Rathmell et al. the entirety of which ishereby incorporated herein by reference. Additionally, the focusing andsteering element 138 may comprise electrostatic deflection plates (e.g.,one or more pairs thereof), as well as an Einzel lens, quadrupolesand/or other focusing elements to focus the ion beam.

The end station 116 then receives the ion beam 124 which is directedtoward a workpiece 130. It is appreciated that different types of endstations 116 may be employed in the implanter 110. For example, a“batch” type end station can simultaneously support multiple workpieces130 on a rotating support structure, wherein the workpieces 130 arerotated through the path of the ion beam until all the workpieces 130are completely implanted. A “serial” type end station, on the otherhand, supports a single workpiece 130 along the beam path forimplantation, wherein multiple workpieces 130 are implanted one at atime in serial fashion, with each workpiece 130 being completelyimplanted before implantation of the next workpiece 130 begins. Inhybrid systems the workpiece 130 may be mechanically translated in afirst (Y or slow scan) direction while the beam is scanned in a second(X or fast scan) direction to impart the beam 124 over the entireworkpiece 130.

The end station 116 in the illustrated example is a “serial” type endstation that supports the single workpiece 130 along the beam path forimplantation. A dosimetry system 152 is included in the end station 116near the workpiece location for calibration measurements prior toimplantation operations. During calibration, the beam 124 passes throughdosimetry system 152. The dosimetry system 152 includes one or moreprofilers 156 that may continuously traverse a profiler path 158,thereby measuring the profile of the scanned beams.

The profiler 156, in this example, may comprise a current densitysensor, such as a Faraday cup, for example, that measures the currentdensity of the scanned beam, where current density is a function of theangle of implantation (e.g., the relative orientation between the beamand the mechanical surface of the workpiece and/or the relativeorientation between the beam and the crystalline lattice structure ofthe workpiece). The current density sensor moves in a generallyorthogonal fashion relative to the scanned beam and thus typicallytraverses the width of the ribbon beam. The dosimetry system, in oneexample, measures both beam density distribution and angulardistribution.

A control system 154 is present that can control, communicate withand/or adjust the ion source 120, the mass analyzer 127, the apertureassembly 133, the magnetic scanner 136, the parallelizer 139, and thedosimetry system 152. The control system 154 may comprise a computer,microprocessor, etc., and may be operable to take measurement values ofbeam characteristics and adjust parameters accordingly. The controlsystem 154 can be coupled to the terminal 112 from which the beam ofions is generated, as well as the mass analyzer 126 of the beamlineassembly 114, the scanning element 136 (e.g., via power supply 149), thefocusing and steering element 138 (e.g., via power supply 150), theparallelizer 139 and the deceleration stage 157. Accordingly, any ofthese elements can be adjusted by the control system 154 to facilitatedesired ion. For example, the energy level of the beam can be adapted toadjust junction depths by adjusting the bias applied to electrodes inthe ion extraction assembly 123 and the deceleration stage 157, forexample.

The strength and orientation of magnetic field(s) generated in the massanalyzer 126 can be adjusted, such as by regulating the amount ofelectrical current running through field windings therein to alter thecharge to mass ratio of the beam, for example. The angle of implantationcan be controlled by adjusting the strength or amplitude of the magneticfield(s) generated in the mass analyzer 126 in coordination with theaperture assembly 133. The control system 154 can adjust the magneticfield(s) of the mass analyzer 126 and position of the resolving aperture134 according to measurement data from, in this example, the profiler156. The control system 154 can verify the adjustments via additionalmeasurement data and perform additional adjustments via the massanalyzer 126 and the resolving aperture 134 if necessary.

FIG. 2 is a diagram illustrating an ion implantation system 200employing a mass analyzer for mass analysis and angle correction inaccordance with an aspect of the present invention. The system 200 isprovided as an example and it is appreciated that other variations andconfigurations can be employed for alternate aspects of the invention.

The system 200 includes an ion source 202 that generates an ion beam204, a mass analyzer 206, a resolving assembly 210, an actuator 214, acontrol system 216, and an angle measurement system 218. The ion source202 can be an arc based source, RF based source, electron gun basedsource, and the like and generates the ion beam 204 along a beam pathhaving a selected dopant or species of ions for implanting. The ionsource 202 provides the ion beam 204 with an initial energy and current.

The mass analyzer 206 is located downstream of the ion source 202 andperforms mass analysis and angle correction on the ion beam 204. Themass analyzer 206 generates a magnetic field that causes particles/ionshaving a selected charge-to-mass ratio to travel along a desired path.The magnetic field can also be adjusted to accommodate for anglecorrections to alter the desired path to yield the angle corrections oradjustments.

Although not shown, a quadrupole lens or other focusing mechanism can bepositioned downstream of the mass analyzer 206 to compensate or mitigatethe impact of beam blow up upon the ion beam 204.

The resolving assembly 210 is positioned downstream of the mass analyzer206. The resolving assembly 210 includes a resolving aperture 212through which the ion beam 204 passes through. The aperture 212 permitsthe selected dopants/species to pass through while preventing otherparticle from passing through. Additionally, the resolving assembly 210can be moved along an axis transverse to the path of the ion beam 204.This permits the resolving aperture 212 to be moved in response tochanges in the desired path of the ion beam through the mass analyzer206. The actuator 214 mechanically moves the resolving assembly 210 suchthat the resolving aperture 212 coincides with a path of the ion beamcorresponding to angle adjustments performed by the mass analyzer 206.In other aspects of the invention, the actuator 214 can also selectother resolving assemblies to accommodate other resolutions and/or othersized beams.

Generally, the resolving aperture 212 is sized to accommodate the beamenvelope of the ion beam 204. However, in alternate aspects, theresolving aperture 212 can be sized to accommodate the beam envelopesacross a range of possible beam paths.

The control system 216 is responsible for controlling and initiatingangle adjustments during ion implantation as well as controlling massanalysis. The control system 216 is coupled to the mass analyzer 206 andthe actuator 214 and controls both components. Another component, theangle measurement system 218, measures angle of incidence values of theion beam and determines needed adjustment angles. The angle measurementsystem 218 can employ Faraday cups or some other suitable measurementdevice to obtain the measured angle of incidence values. Additionally,the angle measurement system 218 can derive or measure an average angleof incidence value for the ion beam 204. The angle measurement system218 then provides adjustment angles or correction values to the controlsystem 216 based on the measured or derived angle of incidence valuesand a desired or selected angle of incidence value.

Initially, the control system 216 sets the magnetic field of the massanalyzer 206 at a nominal or base angle value, such as zero, and aselected charge-to-mass ratio. Additionally, the control system 216 setsthe initial position of the resoling aperture 212 to coincide with anominal path associated with the base angle value. During implantation,a non-zero adjustment angle can be received from the angle measurementsystem 218. Based on the adjustment angle, the control system 216adjusts the magnetic field of the mass analyzer such that the selectedspecies having the selected charge-to-mass ratio travels along analtered patch corresponding to the adjustment angle. Additionally, thecontrol system 216 also adjusts the positioning of the resolvingaperture 212 via the actuator 214 according to the altered path.Thereafter, the angle measurement system 218 can provide additionaladjustment angles for further adjustment of the implant angle.

FIGS. 3A to 3C are views of a portion of an ion implantation provided toillustrate altered beam paths and angle adjustments in accordance withan aspect of the present invention. The views are provided forillustrative purposes and as examples in order to facilitateunderstanding of the present invention.

FIG. 3A is a view 301 of a portion of an ion implantation system inaccordance with an aspect of the present invention wherein an ion beamtravels along a base or nominal path 320.

A mass analyzer 306 is located downstream of an ion source (not shown)and performs mass analysis and angle correction on an ion beam. The massanalyzer 306 generates a magnetic field that causes particles/ionshaving a selected charge-to-mass ratio to travel along a desired path.The magnetic field can also be adjusted to accommodate for anglecorrections to alter the desired path to yield the angle corrections oradjustments. In this figure, the ion beam travels along a base ornominal path 320 associated with the selected charge-to-mass ratio and anominal or zero angle adjustment. A focusing mechanism (not shown) canbe employed downstream of the mass analyzer 306 to compensate ormitigate the impact of beam blow up on the ion beam 304.

The resolving assembly 310 is positioned downstream of the lens 308. Theresolving assembly 310 includes a resolving aperture 312 through whichthe ion beam 304 passes through. The aperture 312 permits the selecteddopants/species to pass through while preventing other particle frompassing through. Additionally, the resolving assembly 310 can be movedalong an axis transverse to the path of the ion beam.

For the nominal path 320, the resolving assembly 310 is placed at anominal position so that the ion beam can pass through the resolvingaperture 312 while blocking other particles from passing through.

FIG. 3B is a view 302 of a portion of the ion implantation system inaccordance with an aspect of the present invention wherein an ion beamtravels along an altered path 322.

The mass analyzer 306 generates a varied field from that shown anddescribed in FIG. 3A in order to alter the path of the ion beam. In oneexample, the mass analyzer 306 increases the magnitude of the magneticfield generated. As a result, the ion beam travels along the alteredpath 322 instead of the nominal path 320. The altered path 322corresponds to a first angle adjustment or offset. The altered path 322passes through the lens 308 and toward the resolving assembly 310.

In this view 302, the resolving assembly 310 is moved in a positivedirection such that the resolving aperture 312 permits passage of theion beam there through along the altered path 322.

Similarly, FIG. 3C is another view 303 of a portion of the ionimplantation system in accordance with an aspect of the presentinvention wherein an ion beam travels along an altered path 324.

Again, the mass analyzer 306 generates a varied field from that shownand described FIG. 3A and FIG. 3B in order to alter the path of the ionbeam. In one example, the mass analyzer 306 decreases the magnitude ofthe magnetic field generated. As a result, the ion beam travels alongthe altered path 324 instead of the nominal path 320. The altered path324 corresponds to a second angle adjustment or offset. The altered path324 passes through the lens 308 and toward the resolving assembly 310.The resolving assembly 310 is positioned in a negative direction, inthis example, such that the resolving aperture 312 permits passage ofthe ion beam there through along the altered path 324 while blocking nonselected species and unwanted particles.

As stated above, the resolving aperture assembly comprises a resolvingaperture through which an ion beam travels. The shape and size of theresolving aperture is generally dependent upon the mass resolution and asize and shape of a desired ion beam, also referred to as the beamenvelope. A larger resolving aperture yields lower beam resolution inthat more unwanted particles and ions can pass through such an aperture.Similarly, a smaller resolving aperture yields greater beam resolutionin that less unwanted particles and ions can pass through such anaperture. However, the higher resolution can also prevent more of theselected or desired species from passing through the resolving aperture,thereby causing undesired beam current loss. Thus, resolving aperturesare typically sized according to a desired mass resolution and beamenvelope.

Additionally, the resolving aperture of the present invention can alsobe designed to accommodate varied beam paths corresponding to a range ofpossible angle adjustments. The above FIGS. 3A to 3C depict someexamples of some possible varied paths. The resolving aperture can beappropriately sized to accommodate such varied beam paths.

FIG. 4 is a side view of a resolving aperture assembly 400 in accordancewith an aspect of the present invention. The view is provided as anexample and is not intended to limit the invention. The assembly 400, inthis example, can accommodate removable plates that allow changing theresolving aperture employed. Additionally, the assembly 400, in thisexample, can operate with varied shaped beams and/or varied massresolutions. Thus different sized beams can be employed within suchsystems and different plates can be employed to accommodate the variedbeam envelopes. Additionally, different plates can be employed toaccommodate for varied resolutions and ranges of angle adjustments.

In FIG. 4, the assembly 400 comprises an arm 402 that holds a resolvingplate 404. The resolving plate 404 includes a plurality of resolvingapertures 406, 408, 410 that selected sizes and shapes, which cancorrespond to selected beam envelopes, selected resolutions, and/orranges of angle adjustments.

The first aperture 406 has a selected size and shape that correspond toa beam envelope, selected resolution, and/or range of angle adjustments.In this example, the x direction of the first aperture is relativelysmall. Thus, for example, the first aperture 406 could accommodate arelatively thin ribbon or scanned ion beam.

The second aperture 408 has a second selected size and a second shapethat correspond to a second beam envelope, a second selected resolution,and/or a second range of angle adjustments. As an example, the secondaperture 408 could accommodate a medium thickness ribbon or scanned ionbeam.

The third aperture 410 has a third selected size and a third shape thatcorrespond to a third beam envelope, a third selected resolution, and/ora third range of angle adjustments. As an example, the third aperturecould accommodate a relatively thick ribbon or scanned ion beam.

It is noted that the y direction for the apertures 406, 408, 410 isdepicted as similar for illustrative purposes, however aspects of theinvention can also include variations in the y direction. Additionally,aspects of the invention can include more or less apertures on a singleplate.

During operation, the assembly 400 is positioned such that one of theapertures is positioned along a path of an ion beam to removecontaminants or unselected material from the ion beam. The selectedaperture corresponds to a selected beam envelope and/or selected massresolution. It is appreciated that materials or portions of the beam maypass through one of the non selected apertures, but those portions arenot generally propagated to a target workpiece.

FIG. 5 is a flow diagram of a method 500 of adjusting the angle ofimplantation in accordance with an aspect of the present invention. Themethod 500 can facilitate uniform angular distribution of ion fluxacross the surface of a workpiece during ion implantation by correctingor adjusting the angle of implant. It is appreciated that the abovefigures and descriptions can also be referenced for the method 500.

The method 500 begins at block 502 wherein parameters of an ion sourceare selected according to a desired specie, energy, current, and thelike. The ion source can be an arc based or non arc based ion source,such as an RF or electron gun base ion source. The specie or species canbe selected by selecting one or more source materials for the ionsource. The current can be selected by modulating power values and/orelectrodes.

Parameters of a mass analyzer are selected at block 504 according to acharge-to-mass ratio corresponding to the selected species and a base ornominal angle. The parameters, such as current applied to coil windings,are set to yield a magnetic field that causes the selected specie totravel along a nominal or base path corresponding to the nominal angleand pass through the mass analyzer.

An initial positioning of a resolving aperture is also selected at block506. The initial positioning corresponds to the base path and permitspassage there through according to a selected mass resolution.

An ion beam is generated as ion implantation is initiated at block 508.An average angle of incidence for the ion beam is obtained at block 510.The average angle of incidence can be measured in one example. Inanother example, multiple beam angle measurements are obtained and anaverage value is derived there from. It is noted that other beammeasurements and angle values can also be employed. For example,calculations of the average angle through an optical train of an ionimplanter can be employed taking into account the effects ofacceleration and/or deceleration whenever applicable.

An angle adjustment is derived from a selected angle of implant and theaverage angle obtained at block 512. For example, if the selected angleis equal to the average angle, the angle adjustment is zero. A magneticfield correction and aperture position correction are determined andapplied at block 514 according to the angle adjustment. The magneticfield correction adjusts the path of the ion beam to correct the angleof the ion beam. The aperture position correction moves the resolvingaperture so that the selected species can pass there through.

It is noted that the angle adjustment and/or magnetic field correctioncan be limited so as to prevent over adjustment. Also, errors in theangle adjustment can be reduced by employing iterative correctionalgorithms. In such instances, suitable angle correction can take anumber of passes.

A corrected average angle of implant is obtained at block 516 afterapplying the field and position corrections. The corrected average angleof implant is obtained as in block 510. If the second average angle isnot sufficiently close to the selected angle of implant or within anacceptable tolerance, as determined at block 518, the method returns toblock 510 and continues iteratively until the average angle of the ionbeam is within the acceptable tolerance of the selected angle.

It is appreciated that the method 500 is described in the above order inorder to facilitate an understanding of the present invention. It isnoted that the method 500 can be performed with other suitable orderingsin accordance with the present invention. Additionally, some blocks canbe omitted and other additional functions performed in other aspects ofthe invention.

Although the invention has been illustrated and described with respectto one or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(blocks, units, engines, assemblies, devices, circuits, systems, etc.),the terms (including a reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component or structure which performs the specified function of thedescribed component (e.g., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary implementations of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one of several implementations,such feature may be combined with one or more other features of theother implementations as may be desired and advantageous for any givenor particular application. The term “exemplary” as used herein isintended to imply an example, as opposed to best or superior.Furthermore, to the extent that the terms “including”, “includes”,“having”, “has”, “with”, or variants thereof are used in either thedetailed description and the claims, such terms are intended to beinclusive in a manner similar to the term “comprising”.

1. An ion implantation system comprising: an ion source that generatesan ion beam along a beam path; a mass analyzer downstream of the ionsource that performs mass analysis and angle correction on the ion beam;a resolving aperture within an aperture assembly downstream of the massanalyzer component and along the beam path having a size and shapeaccording to a selected mass resolution and a beam envelope; an anglemeasurement system downstream of the resolving aperture that obtains anangle of incidence value of the ion beam; and a control system thatderives a magnetic field adjustment for the mass analyzer according tothe angle of incidence value of the ion beam from the angle measurementsystem.
 2. The system of claim 1, further comprising an actuator coupledto the aperture assembly for moving the aperture assembly.
 3. The systemof claim 2, wherein the control system further derives a positionadjustment for the resolving aperture according to the angle ofincidence value of the ion beam from the angle measurement system andthe actuator moves the aperture assembly according to the positionadjustment.
 4. The system of claim 1, wherein the resolving aperture hasa size and shape further according to a range of possible angleadjustments by the mass analyzer.
 5. The system of claim 1, wherein themass analyzer comprises an electromagnet having coils and whereincurrent flowing through the coils is controlled by the control system.6. The system of claim 1, further comprising a second resolving aperturewithin a second aperture assembly having a size and shape according to asecond mass resolution and a second beam envelope, wherein the controlsystem positions one of the aperture assembly and the second apertureassembly along the beam path.
 7. The system of claim 1, wherein theangle measurement system comprises a measurement cup movable across theion beam that measures a plurality of angle of incidence values atplurality of locations.
 8. The system of claim 7, wherein the anglemeasurement system derives the angle of incidence value from theplurality of angle of incidence values.
 9. The system of claim 1,wherein the angle of incidence value is an average angle of incidencevalue across the ion beam.
 10. The system of claim 1, furthercomprising: a magnetic scanner downstream of the resolving aperturecomponent that generates a time varying oscillatory magnetic fieldacross a portion of the beam path; a parallelizer downstream of themagnetic scanner that redirects the ion beam parallel to a common axis;and an end station positioned downstream of the parallelizer componentthat receives the ion beam.
 11. The system of claim 1, wherein thecontrol system derives an angle adjustment from a selected angle ofimplant and the angle of incidence value from the angle measurementsystem and derives the magnetic field adjustment according to the angleadjustment.
 12. The system of claim 1, wherein the magnetic fieldadjustment is limited by a threshold value.
 13. A method of performingion implantation comprising: selecting ion source parameters for an ionsource; selecting an initial magnetic field strength for a mass analyzeraccording to a charge-to-mass ratio; generating an ion beam according tothe selected ion source parameters; performing mass analysis on the ionbeam by the mass analyzer; obtaining an angle of incidence value for theion beam; deriving an angle adjustment value according to the obtainedangle of incidence value and a selected implant angle; and deriving amagnetic field correction according to the derived angle adjustment. 14.The method of claim 13, further comprising setting an initial positionfor a resolving aperture.
 15. The method of claim 14, further comprisingremoving non-selected portions of the ion beam after performing massanalysis.
 16. The method of claim 15, further comprising deriving aposition adjustment value for the resolving aperture according to thederived angle adjustment and applying the position adjustment to theresolving aperture.
 17. The method of claim 13, further comprisingapplying the magnetic field correction to the mass analyzer.
 18. Themethod of claim 17, further comprising obtaining a corrected angle ofincidence value for the ion beam.
 19. The method of claim 18, furthercomprising comparing the corrected angle of incidence to the selectedimplant angle to determine if additional angle correction is needed. 20.The method of claim 13, wherein obtaining the angle of incidencecomprises measuring angles at one or more locations proximate to atarget workpiece.